i guess it depends, I took my mom's 525i to the dealership 4 years ago to get a new muffler put on, and now it needs to be replaced again (it's really bassy, it sets my car alarm off) The car has about 80,000km since the muffler had been replaced. And my mom doesn't really drive it hard (well, not that i know of)
"Driving is like a narcotic, an addiction that can take over lives. It ruins people, breaks families apart, and even kills. Itís habit that needs to be fueled. Time, money, rationality, sweat, knuckle skin, and anyone who disapproves are of little importance to a driver, and are often overlooked. Hi, Iím Nelson, and Iím a drivaholic."